| Luxe Strokes Ltd | Construction | 2025 |
| Luxvision Landscaping Ltd | Construction | 2023 |
| M E London Plumbing & Heating Ltd | Construction | 2022 |
| M S Electrical Limited | Construction | 2016 |
| M Shopfitters Ltd | Manufacturing | 2025 |
| M Whitehead Electrical Limited | Construction | 2017 |
| M&E Power Limited | Construction | 2021 |
| M&H Utilities (AL) Ltd | Construction | 2017 |
| M&M United Limited | Real estate | 2025 |
| M-Team Property Care Ltd | Construction | 2009 |
| M.Nic Group Ltd | Construction | 2014 |
| M.Nic Maintenance Limited | Administrative & support | 2023 |
| M4 Maintenance Limited | Administrative & support | 2025 |
| MA Noula Care Limited | Education | 2025 |
| MA Technology Solutions Ltd | Information & communication | 2025 |
| Macgab Limited | Manufacturing | 2023 |
| Macharose Limited | Wholesale & retail | 2020 |
| Macintyres Ltd | Other services | 2003 |
| MAD Dog Automotive Ltd | Wholesale & retail | 2011 |
| Magnus Johnson Ltd | Information & communication | 2018 |
| Mahantji Limited | Wholesale & retail | 2025 |
| Malcolm Down Publishing Limited | Information & communication | 2014 |
| Maldon Finance Limited | Professional & scientific | 2020 |
| Malibongwe Consulting Ltd | Professional & scientific | 2024 |
| Mandelia International Limited | Information & communication | 2007 |
| Mane Regain Ltd | Wholesale & retail | 2023 |
| Maple Tenon Limited | Professional & scientific | 2018 |
| Marbrook Limited | Health & social care | 2008 |
| Marcoe Construct Limited | Construction | 2023 |
| Marcoe Engineering Limited | Construction | 1999 |
| Marcoe Engineering Services Limited | Professional & scientific | 1996 |
| Marcoe Group Ltd | Financial services | 2025 |
| Marcoe Interiors Limited | Construction | 2024 |
| Mardale Group Limited | Professional & scientific | 2005 |
| Mardat Accomodation Limited | Real estate | 2018 |
| Marel Electrical Limited | Other services | 2014 |
| Mariapolis Limited | Information & communication | 1968 |
| Mark Walker (Grounds Maintenance) Limited | Administrative & support | 2003 |
| Marney Plumbing Limited | Construction | 2025 |
| Marquella Ltd | Health & social care | 2023 |
| Marshall Taylor Property Limited | Real estate | 2020 |
| Marthecarine Ltd | Administrative & support | 2016 |
| Martin Hall (Music) Limited | Other services | 1972 |
| Martin-Woolman Holdings Limited | Financial services | 2020 |
| Martina Angelovicova Limited | Extraterritorial | 2023 |
| Martinfield Management Company Limited | Real estate | 1989 |
| Masala Time Ltd | Hospitality | 2019 |
| Maslin Holdings Ltd | Professional & scientific | 2023 |
| Masq Media Limited | Information & communication | 2024 |
| Masterfit Auto Services & Repairs Ltd | Wholesale & retail | 2017 |
| Masterinnominds Limited | Information & communication | 2014 |
| Masters Contracts Limited | Construction | 2019 |
| Matrix (Inchinnan) General Partner Limited | Professional & scientific | 1999 |
| Matrix Inchinnan RR Limited | Professional & scientific | 2002 |
| Matrix RUM CAY Limited | Real estate | 2021 |
| Matrix Speke Limited | Professional & scientific | 2003 |
| Matrix Spinningfields Limited | Professional & scientific | 2002 |
| Matt Atkins Property Solutions Ltd | Construction | 2026 |
| Matthews & SON (Repairs) Ltd | Wholesale & retail | 2013 |
| Matting Ltd | Wholesale & retail | 2013 |
| Mauya Storytime Limited | Wholesale & retail | 2025 |
| Maxima Business Consultants Limited | Professional & scientific | 2024 |
| Mayachi Ltd | Professional & scientific | 2023 |
| Mbcc Construction Chemicals Limited | Manufacturing | 2022 |
| Mbcc Investments UK Limited | Financial services | 2023 |
| Mccrystal Machinery Limited | Manufacturing | 2024 |
| Mcculloch Financial Management Ltd | Professional & scientific | 2014 |
| Mcduff Security Limited | Administrative & support | 2021 |
| Mcernest Consultancy Ltd | Professional & scientific | 2017 |
| Mcfadden Utilities Limited | Construction | 2011 |
| Mcgrath Management Consultants Ltd | Administrative & support | 2013 |
| MCR Engineering Consultants Limited | Professional & scientific | 2023 |
| MDC Distribution Ltd | Wholesale & retail | 2019 |
| MDM Pyramid Limited | Construction | 2013 |
| Meadowgems Ltd | Professional & scientific | 2020 |
| Mech-Tech Autos Ltd | Wholesale & retail | 2013 |
| MED Progress Ltd | Real estate | 2026 |
| Medexcon Ltd | Professional & scientific | 2024 |
| Medical Taank Ltd | Professional & scientific | 2025 |
| Medxphysio Limited | Health & social care | 2023 |
| Mega UK Choice Limited | Wholesale & retail | 2021 |
| Megalight Technologies Ltd | Construction | 2022 |
| Megaman (UK) Limited | Wholesale & retail | 2000 |
| Mema.B Construction Ltd | Construction | 2019 |
| Merchant Rentals Limited | Financial services | 2002 |
| Mercury AV Ltd | Wholesale & retail | 1992 |
| Mercury Fire Limited | Manufacturing | 2009 |
| Mercury Security Systems Ltd | Manufacturing | 1997 |
| Merrifield Associates Limited | Information & communication | 2002 |
| Meto Global Ltd | Wholesale & retail | 2023 |
| Metro Commercial Printing Limited | Manufacturing | 1998 |
| Mettle Mane Ltd | Wholesale & retail | 2024 |
| Meyer Commissioning Ltd | Professional & scientific | 2021 |
| MFL Projects Limited | Professional & scientific | 2013 |
| MGI Household Services Limited | Construction | 2017 |
| MH Property Holdings Ltd | Financial services | 2022 |
| MHP Food UK Limited | Manufacturing | 2004 |
| MI7 Construction Ltd | Construction | 2021 |
| Miall Smith Limited | Wholesale & retail | 2010 |
| Michael Williams Furniture Limited | Manufacturing | 2018 |